Burning ceramic wares



T. e McDOUGAL BURNING CERAMIC WARES. APPLICATION FILED JULY23. I92I.

Patented May 23, 192?? entr es stares orrrca.

I THE-E 9. MGDOUG-AL 0E FLINT, MICHIGAN, ESSIGNOR T0 CHAMPION IGNEHQN GQWANY, FLINT, MICMGAN, A GORPORATION OF MICHIGAN.

BURNING SWIG WAREQ.

Original application filed October 10, 1919, Serial No. 329,705. Divided and this application filed July 28,

Serial No. $8,135.

a art of this specification.

All

his application is a division of my; United States application Serial No. 329,705,

filed October 10, 1919, to which reference is made for a more complete understanding or the invention.

For the purpose of eliminating the difficulties inherent to the use of periodic kilns, a continuous process has been developed heretofore which. provides for the placing of the saggers or fire-clay slabs upon a refractory car-top and passing the cars through a tunnel from three hundred feet to sixhundred feet'long, comprising a pie-heating, a high-temperature,'and a cooling zone. Vi ith this method the saggers or slabs which support the Ware are piled in mass four to eight feet high on the cars, which travel the length of the tunnel-kiln in not less than twentyfour hours. This method of mass-burning,

while it eliminates the necessity of workmen entering the kiln for loading and unloading purposes, and while it reduces the time of firing somewhat, is nevertheless subject to the loss incident to overfiring and under-firing growing out of the uneven distribution of heat, especially from top to bottom ofthe mass, and to the expense of forming and handling the saggers.

A leading object of the present invention is to provide for both a more rapid and a .more uniform burning of the were than has been attained heretofore, whereby the quality of the goods is improved and the percentage loss incident to even the most approved prior practice is substantially avoided. To this end I burn the ceramic Wares or silicate bodies while exposed openly, preferably in asigle tier only, to the intense heat of a substantially flameless combustion of 'pre-mixed air. and fuel directed against Specification of Letters Patent.

essary for firing is reduced from twenty,

four hours or more in the case of spark plug porceiains to as low as six hours or even less, and a more uniform grade of product is seecured.

A further important object is to enable the heating and cooling steps'to he efi'ected at an increased rate as compared with that necessitated by the use of cars on which both the wares and a large mass of refrac--' tories are necessarily carried. While this may be accomplished in various ways, I prefer to form the ware-supports as thin slabs or trays of highly refractory material which themselves, ride on suitable conveyor-elements of heat insulating material, the necessa body or backing of fire'brickand insulating brick (heretofore carried on the cars) being stationary, In this manner the very large quantity of heat necessarily wasted in the cooling of the large moving mass of the kiln as heretofore constructed is saved, and the time element incident to heating up and cooling down is greatly reduced.

As stated hertofore, the present invention differs from prior practices in that massfir-ing is avoided, and for this purpose the wares are placed on the movable trays or other carriers in a single open tier or so arranged as to be directly subjected to the downward radiation or reflection of heat from the over-lying arch Wall of the tunnel, this well being in turn intensely heated by blasts from burners wherein airand gas fuel or air and oil are premixed in the proper proportion to produce substantially flameless or surface combustion, that is, wherein there is substantially no excess of either air or fuel, or wherein a small excess of oxygen is admitted for the pin ose of burning out organic matter coptaine in the raw porcelain. The articles, for example, spark plug porcelains, are thus subjected directly to the intense heat and vitrify substantially uniformly without the loss incl arch 16, which is here formed of material I ware.

dent to the previous continuous kiln prac-' tice and without the depositing or formation thereon of spots due to unburned fuel.

Figure 1 is a transverse vcross section of a kiln of the continuous type showing a preferred embodiment of the invention.

As more fully indicated in my application above referred to, the kiln comprises three zones, namely, a pre-heating zone, a hightemperature zone, and a cooling zone through which the trays pass from end to end, the temperature of the wares and trays thus being gradually raised in the pro-heating zone to a point where they will safely withstand the highest temperature available,

whereupon they pass into the high-temperature zone; and from the latter to the cooling zone. Both walls of the high-temperature zone are provided throughout their length with upwardly and inwardly inclined passages 15 directed substantially toward the longitudinal mid line of the tunnel dome or of the highest refractory nature; and through these passages the gases or oil fuel and air premixed in substantially such relative proportions that there is enough air and practicallyno more, than is'required to completely burn the fuel is directed in blasts which may easily be made to maintain the dome substantially white hot, in the event spark plug porcelains are being treated, or at a lesser temperature when such is desirable by reason of the nature of the ware, as in the case of enameling or coating iron This flameless combustion generates unusually high heat in an exceedingly 7 small space and has substantially no coloring influence on the ware, although the latter is fully exposed.

In one embodiment of the invention indithe wares are passed through the kiln .on cars of a conventional type, which necessarily include, as a protection for the wheels and other metal work thereof, a large mass or body of refractory and insulating material which 'must be heated up and cooled down at each passage of the car through the kiln, thereby causing costly losses both in' In order to effect a savtime and heat. ing in these particulars, I referably construct the kiln in the general manner shown in the drawing, wherein 5O indicates'suitable'conveyor elements-as shown, rollersconstructed of refractory material such as silicon carbide alundum, zircon or the like upon which the thin refractory. carriers or trays 51, also preferably of the same or 'sim1- lar material, are carried, it being understood thatthere are a series of such rollers spaced from each other longitudinally of the tunnel distances considera ly less than the length of the carriers. The floor of the tunnel is built in close to the over-hanging sides of the trays and between the lines'of conveyor elements with fire brick and insulation brick or material 52 -53, so that, the heat which would pass into a-car body of the conventional type is absorbed by the stationary mass and made use of to heat up the thin oncoming refractory slab or tray. In this connection, it will be understood that the drop in temperature through the tray or carriers 50 is relatively small, the temperature immediately beneath the carrier being too high to permit the use of metal rollers in the high heat zone especially, although metal rollers or conveying mechanism could be employal in parts of the preheating and ooolin zones. In the construction shown the refractory rollers are of sufiicient diameter to protect the shafts 54 on which they are secured, and the latter extend outside the furnace to lubricated bearings 55. By forming the carriers or trays and the wheels with associated bearing and guiding surfaces 56-57 the former are guided properly from end to end of the kiln. Obviously, the rollers may either be of the driven or of the free running type, in which latter case any suitable means for vpushing or propelling the slabs may be provided. Again, while I have shown the re-' fractory conveyor elements in the formof rollers, it is clear that heat insulating eonveyors of different construction, such, for example, as the-reciprocating or step-by-step type, might be used.

From the foregoing it will be understood that the wares in all cases travel through the kiln continuously from end to end whether the movement be constantor step by step, and it is in this sense that the term continuous is employed in'some of the claims.

I claim:

1. In a continuous kiln for burning ce ramic wares, a thin highly refractory carrier forming the'support for the wares, supporting, means on which the carrier travels through the kiln, the space about said supporting-means being filled in with heat insulating material to a level close up tothe lower side of the carrier, said supporting means including a highly refractory element projecting through the floor of the kiln on which the carrier directly rests and 'wlifh reference to which said carrier is mova e. i

' 2. In a continuous kiln having a high-temperature zone, a thin slab-like carrier of highly refractory material von which ceramic wares rest in'open exposure to heat reflected downwardly from thedomeof the kiln, means on which and in respect to which the carrier moves through the kiln, the space beneath the carrier in thehigh-temperature zone being filled in with incombustihle material faced with hi hl refractory material at a level immediate y elow that of the'lower surface of the carrier throughout the larger portion of said surface, the means on which and in respect to which the carrier moves in said high-temperature zone including highly refractory elements projecting slightly above the facing of refractory material and contacting with the carrier, and means, protected from heat by said filled in incombustible and highly refractory material, and immovable longitudinally of said kiln, for supporting said means on which and in respect to which the carrier moves through the kilns.

A 3. In a continuous kiln having a high-tem perature zone, a wide thin carrier of highly refractory material movable through said zone, conveyor elements of highly refractory material spaced apart from one another transversely of the kiln and supporting the carrier, the space between said elements being filled in with heat insulating material substantially up to the level of the lower surface of the carrier, the upper portion of said filling material being of a highly refractory nature.

4. Means for moving a comparatively.

.said means including a conveyor element,

with respect to which said carrier is movable longitudlnally of the kiln, of highly refractory material projecting through the floor of the kiln to contact with the carrier.

5. Means for moving a thin highly refractory carrier through the high-temperature zone of acontinuous kiln, said means including a conveyor element of highly refractory material projecting through the floor of the kilnto contact with the carrier and with reference to which said carrier travels longitudinally of the kiln, a bearing external to the kiln, and a shaft carried in the bearing and supporting said element.

In testimony whereof I afiix my signature.

TAINE G. MoDOUGAL. 

